What are the public IP addresses for Apple Update servers?

I work for a school district and we would like to create a NAT rule in our firewall to make all traffic going out for Apple updates to use the same public IP (iPhones, iPads, Macs, etc). Does anyone know what Apple IP addresses I would need for that?

This will be used to make all devices in our district go to the same Apple Caching Server.

Thanks in advance.